Process for the manufacture of abrasion-resistant shaped coke

ABSTRACT

BRIQUETTES MADE FROM A COKING COAL WITH OR WITHOUT THE ADDITION OF COKE ARE IMMERSED IN A HIGH TEMPERATURE BATH OF PITCH OR THE LIKE. THE BRIQUETTES ARE THEREBY COATED AND IMPREGNATED WITH THE BATH COMPOSITION. THE BRIQUETTES THEN FOLLOW THE NORMAL PROCEDURE OF PASSAGE THROUGH A FURNACE AT A TEMPERATURE SUCH THAT COKING RESULTS. THIS PROCEDURE AVOIDS THE VIOLENT EVOLUTION OF GAS WHICH CAN OTHERWISE OCCUR WITHIN THE COKING FURNACE AND RESULTS IN SHAPED COKE OF HIGH RESISTANCE TO ABRSION.

April 17, 1973 A w REERINK ETAL 3,728,229

PROCESS FOR THE MANUFACTURE OF ABRASION-RESISTANT SHAPED COKE Filed July 29, 1970 uivmon sum FURNACE HEAT HOT INSULATED BRIOUETTE CHAMBR3 PRE-g comma PERFORMED am couvnoa BATH 0F MOLTEN PITCH 0R BITUMEN United States Patent Oflice 3,728,229 Patented Apr. 17, 1973 US. Cl. 201-6 7 Claims ABSTRACT OF THE DISCLOSURE Briquettes made from a coking coal with or without the addition of coke are immersed in a high temperature bath of pitch or the like. The briquettes are thereby coated and impregnated with the bath composition. The briquettes then follow the normal procedure of passage through a furnace at a temperature such that coking results. This procedure avoids the violent evolution of gas which can otherwise occur within the coking furnace and results in shaped coke of high resistance to abrasion.

BACKGROUND OF THE INVENTION In the manufacture of shaped coke it is customary to start with briquettes made from a coking coal with or without the addition of coke. The briquettes are then transferred to a furnace in which they are rapidly raised to the coking temperature; as a result volatiles are ex-' pelled rapidly and the internal pressure developed may be such that the briquettes are disrupted. This difiiculty is particularly severe when the coking is carried out in a sand coker; in this type of equipment the temperature of the briquette is raised suddenly to a minimum of about 900 C. Under such circumstances the volatiles are converted to gas very rapidly and the evolution is violent.

A process which is well known provides for the manufacture of shaped coke on a very economical basis by bringing together one-third portion of bituminous coal and two-thirds of coke. The joining of the two materials is carried out in the pressing operation. The briquettes leave the presses at a temperature of about 400 C. and are then conveyed to the sand coker wherein they are converted to coke. This process suffers from the disadvantage that the abrasion resistance of the material is frequently inadequate for the purpose intended; this is particularly the case during transport as a result of which problems with dusting frequently occur.

Another problem which frequently arises is the breakage of the briquettes during coking operation as a result of vigorous gas evolution internally within the briquettes.

SUMMARY OF THE INVENTION An object of the present invention is a manufacturing process which results in a coke which is abrasion-resistant and relatively dust-free in handling. Another object of the invention is the manufacture of coke briquettes economically and at high speed. Still another object of the invention is the manufacture of shaped coke which retains its shape and is not disrupted or fractured during the coking operation.

According to the present invention, shaped coking coal emerges from hot presses at a temperature between 400 C. and 450 C. This coal is transferred to a bath of hydrocarbon oil or molten pitch in which the shaped pieces are given a coating and are then transferred to a sand coker at a temperature of 900 to 1200 C. The shaped pieces on leaving the presses are preferably held in a chamber insulated against heat loss for a period of 1 to minutes in order to permit evolution of volatiles in the original composition. Surprisingly, it is found that the pretreatment consisting of holding the briquettes at the high temperature for the stated 1 to 5 minute period and the coating by immersion in the hydrocarbon bath are effective in preventing fracture of the shaped pieces during the coking operation and results in shaped coke which is strongly abrasion resistant.

BRIEF DESCRIPTION OF THE DRAWING The single figure is a schematic diagram showing the hot presses, the thermally insulated chamber, the coating bath and a sand-coker.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Briquettes of coking coal leave the hot presses on which they are molded at a temperature of 400 to 450 C. They are then transferred to a high temperature bath of pitch, or bitumen or coal tar. Such materials are complex mixtures of organic compounds containing varying amounts of oxygen, nitrogen and sulfur, etc., in addition to carbon and hydrogen. For the purpose of this disclosure, however, they may be regarded as hydrocarbons since the principal residue after coking is carbon. The term pitch will be used to cover all of the above materials.

There would seem to be a possibility that on making contact between the hot briquettes and the bath, there would be an immediate evaporation of the bath material and consequently the desired effect, namely coating of the briquettes, would not be achieved. Moreover, there is the possibility that after bringing the briquette in contact with the granular heat transfer material of the sand coker the evaporation of the coating material or impregnant might be more rapid than the coking operation. Surprisingly, we have found that if hot briquettes consisting of bituminous coal and coke are dipped into a pitch bath or the equivalent at ZOO-450 C. for a short time, more specifically up to about seconds and preferably between 30 and 60 seconds and if the freshly dipped, essentially uncooled, briquettes are then transferred immediately to a hot heat carrier such as sand in a coker then a product is obtained which is strong and abrasion resistant. Also surprisingly, we have found that it is advantageous to hold the fresh hot briquettes from the presses for a short time such as 1 to 5 minutes under conditions such that the temperature of the briquettes does not fall appreciably prior to introducing said briquettes into the hot bath. The reason is that gases are evolved during this holding period at high temperature which would interfere with the subsequent absorption of pitch. The evolution of gas is originally quite rapid but the rate decays after a few minutes so that any longer delay than about 5 minutes prior to dipping in the hot bath is not useful.

suitable medium for the bath is any material which is liquid at a temperature between ZOO-450 C. and which on coking can comprise a framework for the coking operation itself. Examples are coal tar, coal tar pitch and the bitumen residue from petroleum oil. A preferred impregnant IS the distillation product which accumulates during production of the material used for the hot briquetting. All of these products are strongly absorbed by the hot briquettes so that the briquettes during their transport from the bath to the sand coker present a dry appearance.

The apparatus necessary for carrying out the process according to the invention is shown in the figure. Briquettes at a temperature of 400 to 450 C. are taken from the presses at 1 by the conveyor 2. The conveyor 2 first passes through the chamber 3 which is insulated against heat loss and, if necessary, is heated. While within the chamber for a period of 1 to 5 minutes the briquettes contmue to outgas until the rate of evolution is negligible. The

conveyor then transfers the briquettes to the bath 4 containing a molten pitch or bitumen where the briquettes are impregnated and coated. The briquettes are next taken from the bath by means of the perforated belt conveyor 5 and transferred to an elevator 6. The elevator lifts the briquettes to the top of the shaft furnace 7 where the briquettes encounter the granular heat carrier which will effect the coking. The briquettes pass through the shaft furnace 7 in about 40 minutes.

EXAMPLE 1 Hot briquettes comprised of 25% by weight of a baking coal (28% volatile content) and 75% by weight of fine coke particles (5% volatile content) at a temperature of about 450 C. were passed through a bath of coal tar preheated to 400 C. By means of continual replacement of the consumed binder material with cold coal tar the temperature of the bath was held at aobut 430 C. After an immersion period of about 30 seconds the briquettes were taken rapidly to the sand coker reactor, in which the briquettes encountered the sand at a temperature of 950 C. After 40 minutes in the reactor the shaped coke was drawn off and cooled. In a test in the Micum-Trommel abrasion apparatus, the amount of rub-off was 5.2%; shaped coke prepared without the dipping operation gave a rub-off of 14.5%.

EXAMPLE 2 Briquettes were prepared from 1 part by weight of coking coal (30% volatiles, swelling index 8 /2) and 2 parts by weight of a low temperature coke (2% volatiles) at a briquetting temperature of 480 C. The hot briquettes were taken to an intermediate insulated chamber where they were allowed to stand 3 minutes during which outgasing was essentially completed. They then were taken to a bath of briquette pitch (softening point 70 C.) at 450 C. and immersed. During immersion for 1 minute the briquettes absorbed 7% by weight of pitch. Immediately thereafter the briquettes were transported to the entrance to the sand coker where the briquettes encountered sand at a temperature of 1000 C. The ratio of briquettes to sand was 1:6. The briquettes were allowed 30 minutes for passage through the reactor and then were cooled in a turbulent gas stream.

Samples tested by the Micum-Trommel method gave a rub-off oy 8.4%. The breaking strength as measured by pressing two egg-formed pieces of shaped coke between two plates approaching each other at constant speed was negligibly different from untreated coke shapes. The value for the treated pieces was 260 kp. and for the untreated pieces was 245 kp.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalent of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. Process for the production of abrasion resistant shaped coke comprising the steps of hot pressing in a press briquettes of a coking coal; maintaining after removal from said press the hot pressed briquettes substantially at the temperature they reach during hot pressing for a time period sufiicient to permit outgasing of said briquettes; immersing the briquettes in hot condition in a bath consisting essentially of hydrocarbons maintained at elevated temperature to coat and impregnate the briquettes with said hydrocarbons; and subjecting the thus coated and impregnated briquettes to a temperature sutficiently high to convert said briquettes to coke.

2. Process as defined in claim 1, wherein said briquettes are formed at about 400 C. and are then maintained at a temperature of 400500 C. for a period of 1-5 minutes imediately prior to immersion in said bath.

3. Process as defined in claim 1, wherein said bath is held at a temperature of 200450 C.

4. Process as defined in claim 1, wherein said briquettes are immersed in said bath for a period of /2 to 5 minutes.

5. Process as defined in claim 1, wherein said briquettes are immersedin said bath for a period of 30-60 seconds.

6. Process as defined in claim 1, wherein said molten hydrocarbon bath is comprised of a member of the group consisting of pitches, bitumens and coal tar distillates.

7. Process as defined in claim 1, wherein said bath is comprised of materials capable of forming a coke framework when subjected to coking temperature.

References Cited UNITED STATES PATENTS 3,682,686 8/1972 Nakamura et a1. 117-46 CC 1,549,867 8/ 1925 Graveman 117-46 CB 1,537,190 5/1925 Piron 44-24 3,316,155 4/1967 Holowaty et al 201-6 3,018,227 1/1962 Baum et a1 201-9 X 3,565,766 2/ 1971 Eddinger et a1. 201-23 3,505,201 4/1970 Hodgson 201-23 3,475,278 10/1969 Peters et al 201-12 X 2,948,594 8/1960 Doyle 44-6 1,842,132 1/1932 Trent 208-8 FOREIGN PATENTS 477,770 10/1951 Canada 44--16 NORMAN YUDKOFF, Primary Examiner D. EDWARDS Assistant Examiner US. Cl. X.R.

201-9, 23; 117-46 CC; 44-10 H, 10 K, 6 

